During the Hubble Space Telescope Second Servicing Mission in 1997 and subsequent missions, astronauts detected damage to some of the Telescope thermal insulation. Years of exposure to the harsh environment of space had taken a toll on Hubble protective multi-layer insulation, and some areas were torn or broken. This multi-layer insulation protects the observatory from the severe and rapid temperature changes it experiences as it moves through its 96 minute orbit from very hot sun to very cold night.
Protecting and Maintaining Normal Operating Temperatures
The New Outer Blanket Layer, or NOBL, covers protect Hubble’s external blankets. They prevent further degradation of the insulation and maintain normal operating temperatures of electronics housed in equipment bays. Each NOBL has been tested to ensure that it can withstand exposure to: charged particles, X-rays, ultraviolet radiation, and thermal cycling for at least ten years.
The covers are made of specially coated stainless steel foil which is trimmed to fit each particular door. Each cover is supported by a steel picture-frame structure. Expanding plugs, like common kitchen bottle stoppers, fit into door vent holes to allow quick installation.
During Servicing Mission 3A in 1999, astronauts installed three NOBLS on damaged areas. During Servicing Mission 3B in March 2002, a fourth NOBL was installed. Three additional NOBL panels will be installed during Servicing Mission 4.